Advances in the art of photocopying, digital image scanning and digital printing have made it increasingly difficult to distinguish between an original printed image and a photocopy or scanned-and-printed copy of the original image. These advances have widespread implications regarding secure documents/images including postage indicia, paper currency, bank/traveler checks and/or tickets for various events/entertainment. Inasmuch as such documents/images are assets having monetary value, it will be appreciated that they are vulnerable to counterfeiting by various alteration/copying techniques. To protect or secure these documents/images from such attacks, it is common to introduce “copy detection features” which produce changes relative to the original document/image in a manner that can be readily detected with a high degree of reliability and convenience.
One of the more common “copy detection features” may be found in bank or payroll checks wherein, if copied, a word such as “VOID” or “COPY” appears prominently and/or repeatedly on the face of the copied check. Therein, special thermally-activated ink is employed which blends into the background so as to be practically unnoticeable on the face of the original, however, when the original is copied, the ink is prominently displayed. That is, the heat generated during the photocopying process produces a thermal reaction which causes the ink to give a bold appearance. Hence, a clearly readable message that the check has been copied can be produced to alarm an unsuspecting recipient.
Another example of the use of copy detection features is seen in connection with a postage meter indicia 10 illustrated in FIG. 1. Such indicia 10 are printed on a mailpiece as an indication that the appropriate postage has been paid. Indicia 10 typically include textual information such as the class of mail 12, a postage meter serial number 14, and the postage amount 16. The indicium 10 also includes graphic elements such as a logo 22. Such graphic elements may be printed with copy detection features such as the use of special fluorescent inks. By using inks which fluoresce in the presence of a light source, automated postal equipment can readily identify postage indicia 10 which employ the fluorescing ink, i.e., those printed using a valid postage meter (not shown). In contrast, postage indicia which do not use the fluorescing ink 10, i.e., those copied or scanned/printed, can be identified as being invalid or potentially fraudulent.
It will be appreciated that such copy detection features can be readily incorporated in dedicated/validated postage meters, i.e., those authorized by the United States Parcel Service (USPS) or its designee. That is, authorized postage meters could be equipped with a special print cartridge containing the fluorescing ink. More recently, however, home-based (i.e., Personal Computer-based) postage meter systems have been authorized which make use of commercially available digital printing equipment, i.e., printers fabricated by any one of a variety of manufacturers. Such systems, which print valid postage indicium, have become available through on-line internet service providers, e.g., Netstamps.com offered by Stamps.com, Clickstamp™ Online, etc. While such home-based postage meter systems facilitate the acquisition of valid postage, these systems lack graphic security features, such as the copy detection features, which were previously available through dedicated postage meters.
Concurrently, the USPS has required that postage meter indicia 10 include postal information in machine-readable and machine verifiable format. In FIG. 1, the indicium 10 includes a machine readable, two-dimensional barcode 24 which carries the postage amount and other mailpiece information, such as the class of service. Upon entry into the mail distribution system, it is the barcode 24 portion of the indicium 10 that is automatically read/checked by automated postal equipment. The barcode 24 is provided in accordance with Information Based Indicia (hereinafter “IBI”) standards of the United States Postal Service.
In view of the foregoing, the barcode 24 is essentially the only portion of the indicium 10 where copy detection features can be implemented, inasmuch as the barcode 24 is the only portion of the indicium 10 currently being examined. Further, the barcode 24, as currently configured and implemented, lacks the necessary security features and may be readily be copied. The two attacks which are most probable include:
1) making multiple copies of the indicium 10 without payment.
2) printing a single high denomination indicium to produce multiple copies of the barcode and, subsequently, printing multiple low denomination indicia such that the high denomination barcode may be incorporated into each of the low denomination indicia (replacing each of the low denomination barcodes with the high denomination barcodes by carefully cutting and pasting the two elements together).
Protection against the first attack can be provided by incorporation of an adjacent logo having a robust or fragile watermark, as described in the above mentioned co-pending patent application Ser. No. 10/720,664 “Fragile Watermark for Detecting Printed Image Copies” and Ser. No. 10/720,292 “Detecting Printed Image Copies Using Phase-Space-Encoded Fragile Watermark”, or by use of any other convenient copy detection feature, such as a commercially available Mediasec Copy Detection Pattern.
The second form of attack, i.e., cutting and pasting barcode copies, would seemingly be readily defeated by a simple visual inspection e.g., by a postal service worker using a standard magnifying glass. Unfortunately, the millions of mailpieces processed daily do not facilitate this form of inspection, i.e., such examination being time prohibitive.
Another method to combat this second form of attack is discussed in co-pending commonly owned U.S. patent Ser. No. 11/011,829 entitled, “Method and System for Printing An Original Image and For Determining If A Printed Image Is An Original or Has Been Altered”. This method establishes a correlation or connection between a watermarked logo and an adjacent barcode, which correlation is detectable by automated postal equipment upon induction into the mail distribution system. More specifically, the image or logo includes coded information and a copy detection feature putatively linked to the coded information such that a determination can be made concerning whether the logo and adjacent barcode have been artificially put together, i.e., such as by cutting and pasting.
While this method offers a reliable and traceable solution concerning the alteration of an indicium, the computational requirements to create the linkage for every indicium can be time prohibitive. That is, while the processing time to perform the required steps may take only a fraction of a second, e.g., 0.125 seconds, even such a small increment of time can be prohibitive in a mailing machine that processes over twenty-thousand (20,000) mailpieces per hour. In addition, some mail processing systems have limited processing capability and are not capable of creating the watermark in a reasonable amount of time. Hence, this solution has limited application and can only be used selectively.
A need, therefore, exists for a method for determining whether a printed image (an image having a monetary value, such as postage indicium or paper currency) has been altered or copied with minimal impact on process flow or throughput, i.e., without adversely impacting the speed of commercial transactions.